#include <iostream>
#include <fstream>
#include <deque>
#define Maxx 5000005
using namespace std;
ifstream fin("deque.in");
ofstream fout("deque.out");
deque <int> D;
int A[Maxx],i,n,k;
long long ans;
int main()
{
    fin>>n>>k;
    for (i=1;i<=n;i++)
        fin>>A[i];
    for (i=1;i<=n;i++)
    {
        while (!D.empty() && A[i]<=A[D.back()])
            D.pop_back();
        D.push_back(i);
        if (D.front()==i-k)
            D.pop_front();
        if (i>=k)
            ans+=A[D.front()];
    }
    fout<<ans;
    return 0;
}